Cell membrane HLA-A,B,C and DR like products have been prepared by conventional means from EBV transformed cells homozygous for HLA-D region antigens. The glycoprotein fractions were further purified by immunoprecipitation and affinity chromatography with monoclonal antibodies monomorphic and polymorphic for Class II determinants. Further studies along the same lines with Class II allo-antisera have just now been initiated. The eluted products have been monitored for specificity by two newly developed techniques: inhibition of microlymphocytotoxicity for HLA-DR like activity and inhibition of RIA for cross reactivity with other class II framework monoclonal antibodies. The direction of the project is to ally the structural determinants of Class II antigens revealed by immunochemical techniques with their serologic and cellular functions.